Method and device for producing a tubular solid body from a refractory tungsten heavy metal alloy,  particularly as a semi-finished product for the production of a penetrator for a kinetic energy projectile with fragmentation effect

ABSTRACT

The invention relates to a filler device ( 1 ) comprising an exterior tube ( 2 ) having an extrusion die ( 3 ) located therein and a filler piece ( 4 ) that is filled with a metal powder mixture in the intermediate space ( 8 ) formed between the filler piece ( 4 ) and the extrusion die ( 3 ), whereupon the intermediate space is closed. In order to compact the metal powder, the filler device ( 1 ) is placed in a hydrostatic pressing system and the metal powder mixture is pressed into a green preform. The pressed tubes are subsequently sintered in one or more passes through a furnace, for which purpose the pressed tubes are subjected to a preselected time/temperature progression so as to ensure that a melt of tungsten (W) forms and contracts evenly in all directions so that a geometrically desired solid body results after sintering.

This is a National Phase Application in the United States of International Patent Application No. PCT/EP2008/005800 filed Jul. 16, 2008, which claims priority on German Patent Application No. DE 10 2007 037 702.0, filed Aug. 9, 2007. The entire disclosures of the above patent applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a method and a device for producing a tubular solid body from a refractory tungsten heavy metal alloy, particularly, as a semi-finished product for the production of a penetrator for a kinetic energy projectile with fragmentation effect.

BACKGROUND OF THE INVENTION

Kinetic energy projectiles with a solid penetrator of WSM (tungsten heavy metal) are known. These so-called kinetic energy penetrators are optimized to a maximum penetration depth in armored targets and serve to combat enemy battle tanks.

For specific munitions such as, for example, Penetrator with Enhanced Lateral Effect (PELE), Active Lateral Penetrator (ALP), or Winchester Short Magnum (WSM) explosive projectiles, tubular penetrators are used due to the new requirements for these munitions. These should avoid possible collateral damage of a penetrator, for example, when penetrating a wall, or the like. Such penetrators have previously been produced from solid bars that are subsequently processed by deep-hole boring in order, thus, to be hollowed out or bored through. This method is technically very laborious and not economical.

A method for producing a full penetrator of this type is known, for example, from DE 10 2005 049 748 A1. For the cost-effective production of such a penetrator, a double-funnel filler device matched to the dimension of the penetrator core is inserted concentrically at the outside dimensions of the penetrator, as a result of which an intermediate space is created. While a first tungsten-like powder mixture with a high proportion of tungsten is filled in the inner tube to produce the penetrator core, a second tungsten-containing powder mixture is inserted into the ring-shaped intermediate space, which second powder mixture has a smaller proportion of tungsten than the other powder mixture.

Here, the object of the present invention is to show a more cost-effective method, and a device for carrying out this method, for the production of WSM tubes, as a semi-finished product for the production of, e.g., penetrators for kinetic energy projectiles with fragmentation effect.

SUMMARY OF THE PRESENT INVENTION

The object of the invention is achieved by the features of a first embodiment of the invention or of an eighth embodiment of the invention. Additional advantageous embodiments of the invention are described with respect to the subordinate embodiments. More specifically, in accordance with the first embodiment of the invention, a method for producing a tubular solid body, particularly for producing a penetrator for a kinetic energy projectile with fragmentation effect, is provided and characterized in that (a) a filler device, comprising an outer tube (2) with an extrusion die (3) situated therein as well as a filler piece (4), is filled with a metal powder mixture in the intermediate space (8) forming between the filler piece (4) and the extrusion die (3), and the extrusion die (3) is then closed, (b) in order to compact the metal powder, the filler device (1) is placed in a hydrostatic pressing system and the metal powder mixture is pressed to produce a green preform, and (c) the pressed tubes are subsequently sintered in one or more passes through a furnace, for which purpose the pressed tubes are subjected to a preselected time/temperature progression so that it is ensured that a melt forms and contracts evenly in all directions, so that after the sintering a geometrically desired solid body results.

In accordance with a second embodiment of the invention, the first embodiment is modified so that, after the sintering, the solid body is subjected to a heat treatment, through which tensile strength and elongation at break can be adjusted. In accordance with a third embodiment of the invention, the second embodiment is further modified so that, after the heat treatment, the solid body is subjected to a forging process, through which the flow point and tensile strength increase. In accordance with a fourth embodiment of the invention, the first embodiment, the second embodiment, and the third embodiment are further modified so that the filler device is filled with the metal powder via a filler tube (5) that is placed on the filler piece (4) and enables a filling between filler piece (4) and extrusion die (3). In accordance with a fifth embodiment of the present invention, the first embodiment, the second embodiment, the third embodiment and the fourth embodiment are further modified so that the filler tube (5) is removed after the filling of the filler device. In accordance with a sixth embodiment of the present invention, the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, and the fifth embodiment are further modified so that the intermediate space (8) is closed by a plug (9). In accordance with a seventh embodiment of the present invention, the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, the fifth embodiment and the sixth embodiment are further modified so that the metal powder mixture comprises a tungsten heavy metal alloy with 80-98% by weight tungsten and at least one second component from the group Ti, V, Cr, Mn, Fe, Co, Ni, Mo, or any combination thereof.

In accordance with an eighth embodiment of the present invention, a filler device is provided for the production of a tubular solid body, in particular, a penetrator for a kinetic energy projectile with fragmentation effect, wherein the filler device includes: (a) an outer tube (2) in which an extrusion die (3) and a filler piece (4) are attached concentrically; and (b) a filler tube (5) is placed on the filler piece (4) for filling the intermediate space (8), forming between extrusion die (3) and filler piece (4), with a metal powder mixture. In accordance with a ninth embodiment of the present invention, the eighth embodiment is modified so that the outer tube (2) is a steel tube and the extrusion die (3) is a polyurethane tube.

The invention is based on the concept of producing such tubes or tubular penetrators, both of whose ends can be open or else one can be closed, in a sintering process without reworking the inner contour. The sintering is carried out with an internal medium in the unworked piece that can easily be removed after the sintering. A uniform contraction is achieved by appropriate pressing methods and temperature progressions during the sintering, as is known for solid bars. The material properties are adjusted by the alloy composition and are made more pronounced by heat treatment, as well as optionally by mechanical shaping.

The method can be used for small bars for medium-caliber munitions (e.g., outer diameter 22 mm, inner diameter 15 mm), as sub-caliber large-caliber munitions, and for large bars for full-caliber 120 mm munitions (e.g., outer diameter 120 mm, inner diameter 110 mm). The material is a tungsten heavy metal alloy.

The length and diameter are variable and are currently limited not by the method itself, but rather by the conventional manufacturing plants. However, this has the advantage that available manufacturing plants can be used.

To produce such a tubular solid body, a filler device comprising an outer tube with concentrically arranged extrusion die, as well as a filler piece with a filler tube and centering part placed thereon, is filled with a metal powder mixture. The length and diameter of the outer tube and extrusion die determine the outer contour, and the geometry of the filler piece determines the inner contour of the tubular solid body.

To center the filler piece in the extrusion die, a centering disk of plastic is fixed at one end, and at the other end, the centering takes place via a centering part placed thereon with a filler tube permanently connected thereto. The filler tube enables the cavity between the extrusion die and the filler piece to be filled with a metal powder mixture. After the filler device has been filled up to the upper edge of the filler piece, the centering part is removed from the filler piece together with the filler tube. To produce tubular solid bodies with one closed end, after the removal of the centering part and filler tube, the metal powder mixture is filled by hand up to the desired height above the filler piece. After the filling, the extrusion die is closed with a plug.

To compact the metal powder, the filler device is placed in a pressing system and pressed to form a green preform. Depending on the construction of the filler device, after the green preform has been taken out of the device, the preform has the shape of a tube closed on one side or open on both sides.

After the pressing, the green preform is sintered in one or more passes, as a result of which workpieces with solid body properties are produced from the compact through known measures. For example, tubes for the production of penetrators with very good fragmentation effect are created, which effect can be adjusted via the ratio of inner to outer diameter and the corresponding material or the material composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is to be explained in more detail based on an exemplary embodiment with drawings. The drawings show:

FIG. 1 a, which shows a filler device in the filling state,

FIG. 1 b, which shows the filler device in the filled (closed) state, and

FIG. 2, which shows a tubular solid body produced according to the method with an end closed on one side.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 a, b show a filler device or filler mold 1 for the production of a tubular solid body 10, here closed on one side (c.f., FIG. 2). The filler device, as shown in FIG. 1 a, comprises an outer tube 2 (preferably made of steel), in which bores are situated on the jacket- and base surface at regular intervals. In this outer tube 2, an extrusion die 3 (preferably made of polyurethane), a filler piece 4 (preferably made of metal), and a filler tube 5 are attached concentrically. The concentricity of the filler piece 4 is ensured by a centering disk 6 (preferably made of polyurethane) at the bottom end, and the centering part 7 of the filler tube 5 placed on the filler piece at the top end. The centering part 7 and the filler tube 5 are permanently connected to one another. An intermediate space 8 forming between the extrusion die 3 and filler piece 4 is filled thereby. After the filler device of FIG. 1 a has been filled with the metal powder mixture up to the upper end of the filler piece 4, the centering part 7, together with the filler tube 5, is removed from the filler piece 4 and subsequently metal powder mixture is further filled by hand and the extrusion die is closed with a plug 9 (FIG. 1 b).

In order to compact the metal powder, the filler device as shown in FIG. 1 b is placed in a hydrostatic pressing system (not shown in more detail, since known) and the metal powder mixture is pressed into a green preform at a pressure of approx. 1500 bar. After removal from the filler device shown in FIG. 1 b, the green preform has the shape of a tube closed on one side and can be handled without breaking.

The pressed tubes are subsequently sintered in one or more passes through a furnace (pre-sintering at a temperature between 1400° C. and 1490° C., post-sintering at a temperature between 1495° C. and 1570° C.), so that workpieces with solid body properties are produced from the green preform. For this purpose, the pressed tubes are subjected to a preselected time/temperature progression (i.e., a progression of temperature over time) during the pre- and post-sintering, wherein it is ensured that a melt of tungsten and the remaining binder elements forms in a stable tungsten skeleton, and contracts evenly in all directions, so that after the post-sintering a geometrically desired solid body results, as shown, for example, in FIG. 2.

In order to obtain a material with the desired material properties, after the post-sintering, the solid body is subjected to a heat treatment. E.g., tensile strength, elongation at break, and contraction can be adjusted thereby, depending on the heat treatment. This takes place preferably in an annealing process, in which annealing under high vacuum below the melt temperature of the binder leads to a phase change that, with a subsequent quenching, e.g., in N₂, leads to the fixing of the material state and thus of the material properties.

FIG. 2 shows a tubular solid body for the production of a munition not shown in more detail (for example a kinetic energy projectile with fragmentation effect), which munition has been produced according to the method previously described and has adjusted solid body properties. The munition has, with L_(g), a predeterminable total length and, with L_(v), a length of the solid body, and has an inner diameter d_(i) and an outer diameter d_(a). 

1. A method for producing a tubular solid body, particularly for producing a penetrator for a kinetic energy projectile with fragmentation effect, wherein the method includes the steps of: (a) filling a filler device, wherein the filler device comprises an outer tube provided with an extrusion die situated therein as well as a filler piece, with a metal powder mixture in an intermediate space formed between the filler piece and the extrusion die, and then closing the extrusion die; (b) in order to compact the metal powder mixture, placing the filler device (1) in a hydrostatic pressing system and pressing the metal powder to produce a green perform; and (c) subsequently sintering the pressed tubes in one or more passes through a furnace, for which purpose the pressed tubes are subjected to a preselected time/temperature progression so as to ensure that a melt forms and contracts evenly in all directions, so that after sintering a geometrically desired solid body results.
 2. A method according to claim 1, wherein, after sintering, the solid body is subjected to a heat treatment, through which tensile strength and elongation at break are adjusted.
 3. A method according to claim 2, wherein, after the heat treatment, the solid body is subjected to a forging process, through which flow point and tensile strength increase.
 4. A method according to claim 1, wherein the filler device is filled with the metal powder mixture via a filler tube that is placed on the filler piece and enables a filling between the filler piece and the extrusion die.
 5. A method according to claim 1, wherein the filler tube is removed after filling of the filler device.
 6. A method according to claim 1, wherein the intermediate space is closed by a plug.
 7. A method according to claim 1, wherein the metal powder mixture comprises a tungsten heavy metal alloy with 80-98%, by weight, tungsten and at least one second component selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Mo, and any combination thereof.
 8. A filler device for the production of a tubular solid body, in particular, a penetrator for a kinetic energy projectile with fragmentation effect, wherein the filler device comprises: (a) an outer tube in which an extrusion die and a filler piece are attached concentrically; and (b) a filler tube placed on the filler piece for filling an intermediate space, formed between the extrusion die and the filler piece, with a metal powder mixture.
 9. A filler device according to claim 8, wherein the outer tube is a steel tube and the extrusion die is a polyurethane tube.
 10. A method according to claim 2, wherein the filler device is filled with the metal powder mixture via a filler tube that is placed on the filler piece and enables a filling between the filler piece and the extrusion die.
 11. A method according to claim 3, wherein the filler device is filled with the metal powder mixture via a filler tube that is placed on the filler piece and enables a filling between the filler piece and the extrusion die.
 12. A method according to claim 2, wherein the filler tube is removed after filling of the filler device.
 13. A method according to claim 3, wherein the filler tube is removed after filling of the filler device.
 14. A method according to claim 4, wherein the filler tube is removed after filling of the filler device.
 15. A method according to claim 10, wherein the filler tube is removed after filling of the filler device.
 16. A method according to claim 11, wherein the filler tube is removed after filling of the filler device. 